LODI -- A 13-year-old Henderson School student was arrested for gun possession at Henderson School this morning, the San Joaquin County Sheriff's department said.

The teen, who was on probation for armed robbery, was visited by probation officers for a random check at 9:40 a.m. at the school, in the 13400 block of Extension Road in unincorporated Lodi. Officers found a .22 caliber revolver in his waistband and four unused bullets in his pocket, said Sheriff's spokesman Deputy Les Garcia.

Deputies were called to assist in the arrest, Garcia said. The teen was booked into Juvenile Hall on suspicion of possession of a firearm in a school zone.